The present invention relates to a solenoid valve and, more particularly, to plunger-type solenoid valves which are suitable for use in control systems, control system components, including control valves, pneumatic cylinders or the like, and battery operation, micro processor control and printed circuit board type applications.
Conventional plunger-type solenoid valves includes a housing having a transverse passage formed therein, which is in communication with a primary port, a secondary port and a discharge port. A plunger is received in the transverse passage of the housing for movement along the passage, with the movement of the plunger controlling the communication between the ports to thereby open and close the valve. The movement of the plunger is controlled by an electromagnetic actuator, which is mounted in the housing. When electric current is applied to the electromagnetic actuator, a force is applied to the plunger which moves the plunger along the transverse passage to vary the communication between the ports.
One of the disadvantages of known solenoid valves is their power requirements, which produces as a by-product, undesirable levels of heat during the valve operation. An additional disadvantage to known solenoid valve design is the fact that two magnetic air gaps exist in the magnetic circuit that increase as the stroke of the valve increases. It is understood that the force exerted by the magnetic flux upon the plunger is what causes the plunger to move and close the valve. For a given electrical input, the stronger the magnetic flux present in the magnetic circuit, the longer the valve stroke can be and this is usually accomplished with higher levels of electrical input. Known solenoid valve technology suffers from the fact that as the stroke length increases, both magnetic air gaps increase, thus quickly reducing the flux density of the magnetic circuit and thereby limiting the amount of valve stroke available for a given electrical input. In addition, the cycling rate of conventional solenoid valves is hampered by the residual magnetism that remains after the electromagnetic actuator is de-energized. The residual magnetism delays the movement of the armature thus reducing the response of the valve. In order to increase valve response, larger springs may be employed; however, larger springs require an increase in the magnetic field, hence, increasing the power requirements of the valve.
Typically, these solenoid valves are used to control small volumes of air and, therefore, have small dimensions. Ideally, the size of the valve should be minimized while maximizing the efficiency of the solenoid valves so as to reduce the power consumption thereof. Heretofore, the solenoid valves have employed plunger strokes of about {fraction (1/32)} of an inch. With such stroke requirements, the power requirement of the solenoid valve is quite substantial and may be prohibitive for electronic type applications where the power supply is relative low and/or, further, where the heat generated by such power requirements risk malfunction or destruction of the various electronic devices associated therewith.
Another disadvantage of a typical solenoid valve is that the manufacturing tolerances of the individual parts often exceed the desired stroke size of the valve. As a result, the assembly of such valves has heretofore typically required pre-assembly of each individual solenoid valve so as to permit precise measurement of the actual gap or stroke between the plunger and the valve seat. After the solenoid valve is assembled, the valve is disassembled with suitable adjustments made to reduce or increase the gap to achieve the desired stroke within an acceptable tolerance. As a result, this type of production procedure is extremely time consuming and costly.
Consequently, there is a need for a plunger-type solenoid valve which can operate within desired perimeters while consuming less power than conventionally known solenoid valves thus reducing the heat generation of the valve. Furthermore, there is a need for a solenoid valve that is easier to assemble and, therefore, less costly to manufacture.
The present invention provides a solenoid valve assembly which consumes less power than conventionally known solenoid valves, thus, permitting increased stroke lengths for a given power consumption. With increased stroke lengths, the valve assembly can be assembled in a more cost efficient process.
In one form of the invention, an electrically-operated plunger type solenoid valve assembly includes a housing, with an inlet port and an outlet port, and an electromagnetic actuator positioned in an interior chamber of the housing. The actuator defines a transverse sleeve passage therethrough and is adapted to be selectively energized to generate a magnetic field. An exhaust port body extends into the sleeve passage of the actuator and includes an exhaust passage which defines an exhaust port to provide an exhaust path. A non-magnetic member is positioned in the sleeve passage and has an orifice in communication with the exhaust passage. A plunger is positioned in the non-magnetic member and is supported for reciprocal axial movement in the non-magnetic member between an open position and a closed position. When in the open position, the plunger seals the orifice in the non-magnetic member thereby sealing the exhaust passage, and the inlet port and the outlet port are in communication thereby opening the valve assembly. When moved to the closed position, the plunger seals the inlet port whereby the valve assembly is closed leaving the outlet port in communication with the exhaust port through the exhaust passage. The valve assembly further includes a biasing member which urges the plunger to the closed position. The electromagnetic actuator generates a magnetic field having sufficient magnitude to overcome the force of the biasing member to move the plunger to the open position when the electromagnetic actuator is energized to selectively move the plunger between its open and closed positions to control the communication between the inlet port and the outlet port and the outlet port and the exhaust port. The magnetic forces causing the movement of the plunger are greatly strengthened by the fact that the plunger resides inside the top cap body in such a manner that the magnetic air gap between the two is minimized, fixed and does not change regardless of stroke. It is understood that the force exerted by the magnetic flux upon the plunger is what causes the plunger to move and close the valve. This magnetic force is proportional to the total area of the magnetic air gaps and the square of the magnetic flux density present in the air gap portions of the magnetic circuit. By having the plunger reside inside the top cap body, with the walls of each in close proximity to and parallel to each other axially, and separated by a non-magnetic sleeve, the smaller of the two magnetic air gaps in the magnetic circuit is effectively kept at a fixed minimum regardless of stroke. The effective of this orientation is to greatly increase the magnetic flux density in the remaining larger area air gap in the magnetic circuit. This in turn produces very large increases in magnetic force upon the plunger especially at longer distances, and allows longer strokes without having to increase electrical input. The non-magnetic member provides a magnetic gap between the plunger and the electromagnetic actuator and exhaust port body to magnetically isolate the plunger from a residual magnetic field remaining in the electromagnetic actuator and the exhaust port body after the electromagnetic actuator is deenergized energized thereby forming a quick response valve.
In one aspect, the electromagnetic actuator includes a spool, which defines the transverse sleeve passage. Preferably, the electromagnetic actuator includes a wire that is coiled around the spool and extends between end flanges of the spool. In other aspects, the valve assembly further includes a coil frame which supports the spool in the interior chamber of the housing.
In other aspects, the plunger has a generally T-shaped configuration having a cylindrical stem and a flange. The stem extends into the sleeve passage and has a first sealing surface to seal the orifice of the non-magnetic member when the plunger is moved to the first position. The flange includes a second sealing surface for sealing the inlet port when the plunger is moved to the second position. Preferably, the stem and/or the flange includes a seal member to provide the respective sealing surfaces. For example, the plunger may include a longitudinal passage and a unitary seal positioned in the passage, which provides both sealing surfaces.
In other aspects, the non-magnetic member includes a generally cup-shaped body having a portion extending into the exhaust port body and receiving a portion of the plunger whereby the plunger is in close proximity to the exhaust port body. In further aspects, the generally cup-shaped body includes a sleeve portion, which is spaced from the plunger and forms a cavity therebetween. The biasing member is positioned in the cavity and urges the plunger toward the valve seat insert to seal the inlet port. In yet further aspects, the valve assembly includes a valve seat insert which includes an inlet opening and an outlet opening, which are in communication with the inlet and outlet ports, respectively. In addition, the cup-shaped body includes a third portion, with the valve seat insert extending into and being seated in the third portion of the non-magnetic member to provide a compact assembly.
In another form of the invention, an electrically operated plunger-type solenoid valve assembly includes a housing, a base with an inlet port and an outlet port, a coil assembly, and an exhaust port body. The coil assembly is positioned in the housing and is adapted to be selectively energized to generate a magnetic field and has a transverse sleeve passage. The exhaust port body extends into one end of the sleeve passage and has an exhaust passage extending therethrough, with the exhaust passage defining an exhaust port. A non-magnetic member is positioned in a second end of the sleeve passage, with the non-magnetic member having an orifice in communication with exhaust passage of the exhaust port body. The valve assembly further includes a valve seat insert which is recessed in the non-magnetic member in the housing and includes an inlet opening and an outlet opening, which are in communication with inlet and outlet ports, respectively. A plunger is positioned in the non-magnetic member between the orifice of the non-magnetic member and the valve seat insert and is supported for reciprocal axial movement in the sleeve passage between an open position wherein the plunger is spaced from the valve seat to permit communication between the inlet and outlet ports and wherein the plunger seals the orifice of the non-magnetic member thereby sealing the exhaust passage, and a closed position wherein the plunger seals the inlet port whereby the valve assembly is closed. The biasing member applies a force to the plunger to urge the plunger to its closed position, with the coil assembly generating a magnetic field having sufficient magnitude to move the plunger against the force of the biasing member to move the plunger to its first position when the coil assembly is energized to selectively move the plunger between its open and closed positions to control communication between the inlet port, the outlet port, and the exhaust port. The plunger, biasing member, and valve seat insert are positionable in the non-magnetic member to provide a simplified assembly process.
In one aspect, the non-magnetic member comprises a cup-shaped liner. For example, the cup-shaped liner may be formed from a non-magnetic stainless steel. In other aspects, the liner preferably has a thickness in a range of 0.003 to 0.007 inches.
In other aspects, the exhaust port body includes a recessed annular surface extending around the opening of the exhaust passage which defines a recess. A portion of the non-magnetic member extends into the recess to provide a close fit between the plunger and the exhaust port body.
In other aspects, the biasing member comprises a spring, and the non-magnetic member defines a spring cavity adjacent the plunger. The spring is positioned in the spring cavity to urge the plunger to its second position.
It can be appreciated from the foregoing that a solenoid valve assembly is provided that isolates the plunger from the effects of the residual magnetic field that remains even after the coil assembly is de-energized. As a result, the valve can operate with lower power consumption and with greater speed. In addition, the stroke size may be increased while maintaining the power consumption at acceptable levels. Furthermore, with increased stroke lengths, the valve assembly can be manufactured in a more efficient manner, thus reducing the cost of the valve assembly.
These and other objects, advantages, purposes, and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings.